A Nature Made City

author
An article on wall trees in hongkong
article, Asian coalition of architecture and urbanism (acau)
2017

I remember sitting on the bus towards Hong Kong Island and seeing the rolling green mountains surrounding the city, one could assume that they would be stepping into a green metropolis comparable to places like Singapore, where the city centre is weaved with trees, and maybe, all those photos of dense residential were just selective views of part of the city.

Green in Hong Kong however, stops at the boundaries between city and the mountains. The places where people live and work in – from the high-rise housing estate of Tseung Kwan O, to the shopping malls of Causeway Bay and the office towers of Central – are anything but green. If anything, the greenery in various buildings are merely visual features, with the smattering of potted foliage and planters scattered sparingly.

Hong Kong is extremely concrete in fact. The lack of nature in the city itself has built up a severe disconnect with the wild side of Hong Kong, compounded as the city grew larger, with a perspective of the dangers which nature might bring being blown out of proportion - in one case, residents fearing that the planting of trees would help spread bird flu and dengue. With approximately 7,197 people per square kilometre, Hong Kong is one of the most densely populated places in the world. Due to the natural terrain on which it sits, mostly mountainous and hilly, the city has no choice but to make use of all the flat land it can get, both natural and reclaimed. As a result Hong Kong’s urban spaces are densely packed with concrete and asphalt, with nature taking a back seat in the allocation of space. 50% of Hong Kong consists solely of roads and parking facilities; all this excluding high-rise buildings.

However, while wild nature may have been kept in the backyard of the city, there is another form of nature that take root, and that is of “man-made” nature. It is a kind of nature which involves nature’s methods of adaptation combined with human ingenuity to help the city function on such a difficult terrain. Wall Trees in the City. Wall Trees - generally Chinese Banyans - have been found on top of large masonry retaining walls with its roots carving into its fissures and cracks, they’ve been seen as a natural substructure to the bottom of buildings.

In the midst of Hong Kong’s urban growth, it became necessary to cut into the slopes of the hills to create more usable space. This included space for the building of roads as well, and most of the 1,200 Wall Trees were actually part of the solution proposed by the British government in the 19th and 20th century to strengthen the integrity of its vertical retaining walls, despite the common belief that the trees had taken root by themselves. To give true credit, the idea of growing trees directly into walls originated from Guangdong Masonry workers in the 1800’s. With the trunk base situated within the confines of the walls, its spreading roots help stabilize the soil, soak up and transpirate large amounts of water accumulated behind terraces finally alleviating pressure on the stone-work. Together the root strength of the trees with the development of 1,700 masonry retaining walls lessened the likelihood of slope failure throughout the Western and Central parts of Hong Kong, making it possible for the city’s existence within such hilly terrains.

Held tight in our roots
A city growing fast
Learning to let go

Smog, fog, all things bad
Nervous anticipation
What will become of us

Stonewall trees denote a special if not unique urban ecological endowment of Hong Kong. Very few places in the world have so many stone retaining walls concentrated in a relatively small area, and with so many trees of sizeable biomass and high landscape quality to dwell on them.

They represent the product of a difficult terrain working in tandem with human labour and ingenuity in creating a city literally from scratch. At the same time, due to the naturally long lifespan of trees, it is no wonder people grow attached to them as well, in some cases even mourning the loss of some trees from felling. In a way, as the trees are felled, memories of the surrounding places within people die with them. Beyond landscaping and ecological effects, there is a much more intangible quality by having nature in the city.

Despite that, the cracks between nature and city shows itself through falling Wall Trees as the city forces them to grow within smaller confines and continues to push its boundaries further into the hills, requiring them to have more excessive maintenance. There is only that much nature can do when a city continuously extends its boundaries beyond its natural reach.

Even in “man-made” nature, a kind of balance still has to exist between concrete and earth.